Poolmaster 52557 18" Clock/ Thermometer/Hygrometer - White 3-in-1 clock for indoor or outdoor use Clock, thermometer, and hygrometer for measuring humidity Weather-resistant with durable metal frame with baked enamel finish Clock features battery-operated quartz movement (batteries not included) Large easy-to-read roman numerals Battery-operated - requires 1 AA battery (battery not included) 18" diameter